Personal computers, as shown in FIGS. 1 and 2, include a monitor 100, keyboard input 102 and a central processing unit 104. The processor unit typically includes a microprocessor 106, a memory bus circuit 108, and other peripheral circuitry 110. The memory bus is provided with a number of expansion sockets to allow the purchaser of the personal computer to install additional memory circuits as the user's needs change. A number of expansion sockets for memory upgrades typically exist along a memory bus. The expansion sockets remain empty unless the user decides to upgrade the system's memory by installing additional memory circuits.
In general, the characteristic impedance of the computer's memory bus interface is designed to match the impedance of a fully loaded memory bus. When the memory bus is fully loaded, therefore, the interface and the bus will be matched. The mismatch in impedance creates a ringing effect on the memory bus which results in overshoot and undershoot in a signal communicated over the bus. Such ringing has not created difficulty in communicating with typical memory circuits. This is due to the limited communication speeds of memory circuits used to-date. Memory circuits, however, are being designed which can operate at increasingly faster communication speeds.
Computers which have a memory bus and memory bus interface where the impedance therebetween is mismatched can experience errors in communication when fast data rate memory circuits are installed in a partially empty data bus. Further, as the population of a bus changes, the electrical Termination must change accordingly.
For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for an electrical socket which adjusts the electrical termination characteristics if the socket is populated.